<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
    <script src="js/callback.js"></script>
</head>
<body>
    <button>隐藏</button><p>hello world! hello world!</p>
</body>
</html>